A viral video is gaining popularity on the Internet in which one of the protesters in Hong Kong in a few seconds neutralized a smoking tear gas canister with a thermos filled with ordinary dirt.
Popular Mechanics asked Sven Eric Jordt, a specialist in pharmacology and toxicology at Duke University, to comment on the video. According to him, the contents of a tear gas can is very similar in composition to fireworks.
The new way Hong Kong protesters deal with tear gas
When ignited, a piece of charcoal ignites inside the can, and chemical compounds such as potassium nitrate and chlorate release oxygen, which feeds the flame. In particular, potassium nitrate helps the coal burn faster. In turn, potassium chlorate decomposes to form gaseous potassium chloride.
Silicon is sometimes added to the mixture to help the gas form droplets. Magnesium carbonate maintains a mildly acidic environment in the cartridge to avoid destabilizing the potassium chlorate.
Another "secret" ingredient is sugar. Sucrose burns at low temperatures and helps turn a key ingredient in tear gas into toxic vapor. This is 2-chlorobenzalmalononitrile or CS.
All of these ingredients are bound in a canister by a sticky, flammable compound called nitrocellulose. Tear gas causes coughing, respiratory inflammation, eye burns, and even asthma attacks.
Can street dirt be used to neutralize tear gas, as the participant in the video does? Jordt states that "this will extinguish the burning components, block the oxygen supply to the cartridge and close the aerosol exit holes." However, the scientist did not give an exact answer. Perhaps the smoking can was neutralized simply by being placed in an airtight thermos.